An intelligent completion system can both characterize and control the reservoir fluids flowing within a given compartment of the system. For example, the system may use a venturi and its associated differential pressure of the fluid to monitor the flow rate, and a capacitance sensor to measure the water cut (volumetric ratio of water produced to total liquids produced). Existing systems are generally limited, however. For example, such systems may be limited to water cut measurements in a range up to phase inversion, or may fail to include the detection of gas ingress. Nuclear-based flow metering is an alternative measurement means, but such tools are sometimes not available. For instance, some applications or users preclude/forbid the use of a nuclear source. Pyroelectric x-ray generators are known, but current implementations tend to yield inadequate signal-to-noise ratios due to, for example, limited photon flux, limited photon energies, and poor source stability and control. Cost-effective true three-phase downhole flowmeters are an aspiration, which is yet to be fully realized by the industry